Differential signaling is a way of transmitting a differential signal from a transmitter to a receiver via a differential transmission line, e.g., via a pair of wires, e.g., copper wires. A differential signaling driver circuit drives an electrical current through the transmission line in accordance with a driver signal. The electrical current in the transmission line is referred to herein as the signal current. The driver signal may, for example, be provided by a voltage, an electrical current or any other suitable physical quantity.
A differential signaling receiver circuit may comprise a resistive bridge connected across the differential output of the transmission line, i.e., between the two conductors of the transmission line at the end of the transmission line. The electrical current injected into the transmission line by the differential signaling driver circuit thus translates into a voltage across the resistive bridge at the end of the transmission line. This voltage may be further processed or analysed by the differential signaling receiver circuit or by circuitry connected to the differential signaling receiver circuit.
The driver signal is usually a bi-level signal, i.e. a binary signal. However, a differential signaling driver circuit may, in principle, be capable of translating any kind of waveform of the driver signal into a corresponding waveform of the signal current. In other words, a differential signaling driver circuit may be suitable for both continuous (i.e., analogue) and discrete (i.e., digital) driver signals.
Differential signaling may be performed in a low-voltage manner when a differential signal of low voltage amplitude is superimposed on a common mode DC voltage. For example a differential signal with a maximum amplitude of 0.5 V or less, e.g. 350 mV may be imposed on a common mode voltage of 1.5 V or less, such as 1.2 V or less, e.g. 0.9 V or less, e.g. 0.4 V. This is generally referred to as LVDS, for which several different standards have been developed, such as IEEE 1596.3, ANSI/TIA/EIA-644-A and several variations such as M-LVDS, sub-LVDS, etc.
Differential signaling driver circuits are described, for example, in U.S. Pat. No. 7,034,574 B1 by Li and U.S. Pat. No. 7,304,494 B2 by Wong et al.